154,057 research outputs found
Counting problems for special-orthogonal Anosov representations
For positive integers and let be the
projective indefinite special-orthogonal group of signature . We study
counting problems in the Riemannian symmetric space of and in the
pseudo-Riemannian hyperbolic space . Let be
a totally geodesic copy of . We look at the orbit of
under the action of a projective Anosov subgroup of . For certain
choices of such a geodesic copy we show that the number of points in this orbit
which are at distance at most from is finite and asymptotic to a purely
exponential function as goes to infinity. We provide an interpretation of
this result in , as the asymptotics of the amount of
space-like geodesic segments of maximum length in the orbit of a point.Comment: To appear in Ann. Inst. Fourier. 40 pages, 1 figur
Data Augmentation in the Bayesian Multivariate Probit Model
This paper is concerned with the Bayesian estimation of a Multivariate Probit model. In particular, this paper provides an algorithm that obtains draws with low correlation much faster than a pure Gibbs sampling algorithm. The algorithm consists in sampling some characteristics of slope and variance parameters marginally on the latent data. Estimations with simulated datasets illustrate that the proposed algorithm can be much faster than a pure Gibbs sampling algorithm. For some datasets, the algorithm is also much faster than the efficient algorithm proposed by Liu and Wu (1999) in the context of the univariate Probit model
Geometric aspects of nonholonomic field theories
A geometric model for nonholonomic Lagrangian field theory is studied. The
multisymplectic approach to such a theory as well as the corresponding Cauchy
formalism are discussed. It is shown that in both formulations, the relevant
equations for the constrained system can be recovered by a suitable projection
of the equations for the underlying free (i.e. unconstrained) Lagrangian
system.Comment: 29 pages; typos remove
Nanoformas de carbono moleculares quirales
Conferencias científicasCharla magistral sobre la química en fullerenos quirales y sus propiedades.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech.
Vicerrectorado de Investigación de la Universidad de Málag
Spin bath dynamics and dynamical Renormalization Group
Abstract We discuss the quantum dynamics of the central spin model in a
regime where the central spin and bath are slaved to each other. The exact
solution is found when the bath is static, and is compared with the effect of
an external field, finding that they are inequivalent due to the quantum nature
of the environment. When the bath has dynamics, we analyze the differences
between the numerical simulation using time-dependent perturbation theory and
the equation of motion technique, which shows better accuracy. We demonstrate
that the use of dynamical Renormalization Group (dRG), simultaneously with the
equation of motion technique, provides a suitable analytical tool to understand
the physics, to capture the main physical processes, and a powerful method to
eliminate secular terms. In addition, this approach allows to separate
classical non-linear behavior from corrections due to quantum correlations.Comment: Main text and Appendi
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